Variable sine wave generator

[1insuare]

Hello again,

you were very kind with me the first time I wrote a post so I will try again!!

This time I am trying to build a sine wave oscillator with analog components, ICs,etc.

The output signal must be 0 to 5V and the frequency must be programmable or variable between 1 kHz and 20kHz.

If you have any idea or come up with any circuit in LTSpice IV let me know please.

Thank you very much indeed in advance.

Rob

 

[Jaguarjoe]

I don't know about LT spice, but start with "Wein bridge" oscillators and go from there if you want a discrete solution. Maintaining the loop gain at 1 is a challenge. Hewlett & Packard figured that out in the 30's. Look at HP now.
There maybe chips around like the old XR2206 and older 8038 that could do this too. Thomas Henry has a nice 8038 design that will do what you want and more.

 

[JimB]

Generating a sinewave at a fixed frequency is fairly simple.
A wien bridge or phase shift oscillator circuit will work well.

The problems start when you want a wide range of frequencies, the attenuation in the frequency determining network changes and keeping the loop gain at 1 (to maintain oscillation without introducing distortion) gets awkward.
Thermistors or incandescant lamps have been used in the past to adjust the gain.

You are asking for a 1khz to 20khz frequency range, depending on the circuit used, this could be difficult if not impossible to do with out range switching.

Commercial function generators seem to start by generating a triangle wave and then converting that to a sinewave using a shaping circuit.

As Jaguarjoe has suggested, using an IC such as the XR2206 or 8038 or one of its variants is a quick and easy way if you want to stick to the analogue world.

If you want to do 1 to 20khz in one range, consider a heterodyne technique, beating two high frequency oscillators together to create a lower frequency.
Or, more practically, go digital and use a Direct Digital Synthesiser (DDS).

JimB

 

[Ratchit]

1insuare,

You might want to look at the link below. It gives the schematic and design equations for a Wein-bridge that only needs one adjustable resistor to vary the frequency.

https://www.electro-tech-online.com/threads/variable-sine-wave-generator-design.99236/ See posts 31 and 36.

Ratch

 

[JimB]

Ratchit

Interesting circuit, I did not know about that one.

Thank you

JimB